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The Sources and Origin of Magmas
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
E.V. Sharkov, O.A. Bogatikov, V.I. Kovalenko
Irrespective of these different viewpoints, the guiding mechanism of crustal generation is believed to be anatexis caused by low-temperature eutectic melting of granites from rocks of intermediate and acid composition, including metamorphosed sedimentary rocks (Mehnert, 1968; Mitrofanov, 1985; etc.). Detailed studies conducted under the guidance of Glebovitsky and Mitrofanov (Mitrofanov, 1985) have demonstrated that the process (cycle) of granite formation proceeded in a definite sequence, including the following events: the formation of early Na-granitoids;multi-stage anatectic migmatization concomitant with continuous overall deformation and resulting in the formation of acidic magma sources;the formation of late K–Na or K-granitoid complexes, usually with indications of intrusive origin due to the deep-seated crustal sources or mature differentiation of anatectic or diatectic magmas. This cycle of granite formation generally continued for some 5–10 Ma.
Igneous Petrology and the Nature of Magmas
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Melting can only occur if temperature exceeds the solidus, and temperatures rarely, if ever, reach the liquidus. Because the geothermal gradient is different in different places, this means that partial melting occurs but does not occur everywhere. So, magmas generally form by melting of an originally solid parent rock that does not melt completely. When a rock melts only partially, producing a melt that contains melted low-temperature minerals and leaving behind solid high-temperature minerals, we call the process anatexis. In the mantle, for example, anatexis of ultramafic rock produces basalts.
Geological setting of exceptional geological features of the Flinders Ranges
Published in Australian Journal of Earth Sciences, 2020
The British Empire Granite (Figure 18) intruded the Mount Painter Inlier well after cessation of the Delamerian Orogeny. This event is thought to be due to mid-crustal anatexis being provided by the unusual instance of burial of the high radiogenic heat-producing basement rocks beneath insulating Neoproterozoic cover sediments (Hore & Cowley, 2015), although magmatic heat input cannot be ruled out. The British Empire Granite is the only known instance of melting of pre-existing rocks thought by most geologists to be caused primarily by trapped radiogenic heat (Government of South Australia, 2017).